title: Functional phosphoproteomic analysis reveals cold-shock domain protein A to be a Bcr-Abl effector-regulating proliferation and transformation in chronic myeloid leukemia.
abstract: One proposed strategy to suppress the proliferation of imatinib-resistant cells in chronic myeloid leukemia (CML) is to inhibit key proteins downstream of Bcr-Abl. The PI3K/Akt pathway is activated by Bcr-Abl and is specifically required for the growth of CML cells. To identify targets of this pathway, we undertook a proteomic screen and identified several proteins that differentially bind 14-3-3, dependent on Bcr-Abl kinase activity. An siRNA screen of candidates selected by bioinformatics analysis reveals cold-shock domain protein A (CSDA), shown previously to regulate cell cycle progression in epithelial cells, to be a positive regulator of proliferation in a CML cell line. We show that Akt can phosphorylate the serine 134 residue of CSDA but, downstream of Bcr-Abl activity, this modification is mediated through the activation of MEK/p90 ribosomal S6 kinase (RSK) signaling. Inhibition of RSK, similarly to treatment with imatinib, blocked proliferation specifically in Bcr-Abl-positive leukemia cell lines, as well as cells from CML patients. Furthermore, these primary CML cells showed an increase in CSDA phosphorylation. Expression of a CSDA phospho-deficient mutant resulted in the decrease of Bcr-Abl-dependent transformation in Rat1 cells. Our results support a model whereby phosphorylation of CSDA downstream of Bcr-Abl enhances proliferation in CML cells to drive leukemogenesis.
authors.affiliation: Cell Survival Signalling Laboratory, Centre for Molecular Oncology and Imaging, Institute of Cancer, Barts and the London School of Medicine, Queen Mary University of London, UK.
authors.forename: D
authors.initials: D
authors.lastname: Sears
authors.forename: P
authors.initials: P
authors.lastname: Luong
authors.forename: M
authors.initials: M
authors.lastname: Yuan
authors.forename: G
authors.initials: G
authors.lastname: Nteliopoulos
authors.forename: Y K S
authors.initials: YK
authors.lastname: Man
authors.forename: J V
authors.initials: JV
authors.lastname: Melo
authors.forename: S
authors.initials: S
authors.lastname: Basu
mesh_terms: D048948:14-3-3 Proteins / Q000378:metabolism; D000970:Antineoplastic Agents / Q000627:therapeutic use; D001549:Benzamides; D022762:CCAAT-Enhancer-Binding Proteins / Q000378:metabolism*; D049109:Cell Proliferation; D002471:Cell Transformation, Neoplastic; D016044:Fusion Proteins, bcr-abl / Q000378:metabolism*; D006360:Heat-Shock Proteins / Q000378:metabolism*; D006801:Humans; D000068877:Imatinib Mesylate; D015464:Leukemia, Myelogenous, Chronic, BCR-ABL Positive / Q000188:drug therapy / Q000378:metabolism*; D013058:Mass Spectrometry / Q000379:methods*; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D010748:Phosphopeptides / Q000032:analysis*; D010766:Phosphorylation; D010879:Piperazines / Q000627:therapeutic use; D020543:Proteome / Q000032:analysis*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D011743:Pyrimidines / Q000627:therapeutic use; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D038744:Ribosomal Protein S6 Kinases, 90-kDa / Q000378:metabolism; D015398:Signal Transduction; D014407:Tumor Cells, Cultured
chemical_list: D048948:14-3-3 Proteins; D000970:Antineoplastic Agents; D001549:Benzamides; D022762:CCAAT-Enhancer-Binding Proteins; D006360:Heat-Shock Proteins; D010748:Phosphopeptides; D010879:Piperazines; D020543:Proteome; D011743:Pyrimidines; D034741:RNA, Small Interfering; C094867:YBX3 protein, human; D000068877:Imatinib Mesylate; D016044:Fusion Proteins, bcr-abl; D051057:Proto-Oncogene Proteins c-akt; D038744:Ribosomal Protein S6 Kinases, 90-kDa; D020929:Mitogen-Activated Protein Kinase Kinases